Tool for roughening a borehole surface

ABSTRACT

A tool for roughening a borehole surface. The tool includes a coupling portion for clamping the tool in a drilling machine; and a tool head for machining the borehole surface, where the tool head comprises a cutter that is circumferentially disposed on the tool head, and where the tool head has at least one slit, which passes through from one side to the other and which, starting from an end face of the tool head, and extends axially along a longitudinal axis of the tool.

BACKGROUND OF THE INVENTION

The invention relates to a tool for roughening a borehole surface, witha coupling portion for clamping the tool in a drilling machine and atool head for machining the borehole surface, wherein circumferentiallydisposed cutting means are provided on the tool head.

For fastening building parts to foundations, it is known to fix profiledanchor bars by means of a chemical mortar compound in blind holesalready drilled into the foundation. The blind holes can be drilled bymeans of diamond-surfaced tools. Depending on the material of thefoundation, the borehole wall of such a borehole may be very smooth. Inorder to transfer even high tensile forces acting on the anchor barsreliably to the foundation, it is of advantage when the mortar compoundin the cured condition interacts interlockingly with the borehole wall.This can be achieved by mechanically roughening at least part of theborehole wall or by providing it with profiling.

Tools and methods of the type mentioned in the introduction forroughening a borehole surface are therefore used in particular toincrease the load-bearing capacity of chemical mortar compounds indiamond-drilled holes. In the process, the relatively smooth inner shellsurface of a borehole is structured and, for example, provided withdefined undercuts.

Various concepts are known for introducing such undercuts in a boreholesurface. For example, DE 31 43 462 A1 and DE 38 19 650 A1 respectivelydescribe tools on the tool shank of which a conical or cambered contactface is provided, to enable a user to superpose a wobbling motionmanually on the tool rotation. In this way, the tool head is deflectedin radial direction and penetrates into the borehole surface.

Furthermore, it is known from DE 103 34 150 A1 how to dispose a toolhead eccentrically on a tool shank and in this way to achieve radialdeflection of the cutters disposed circumferentially on the tool head.

DE 196 10 442 A1 proposes an asymmetric arrangement of tool cutters, sothat the tool has an imbalance that generates a wobbling motion duringdrilling operation.

The already known solutions suffer from the disadvantage that both theoperator and the drilling machine are greatly stressed by vibrations dueto the wobbling motion of the tool. In addition, the result of theroughening process depends on the duration of application as well as onthe machine guidance by the respective user. Furthermore, the cuttingelements normally used for roughening, such as carbide or diamondcutting members, are exposed to severe wear, especially when theyencounter rebar or hard rock during the roughening process.

SUMMARY OF THE INVENTION

Against this background, the technical problem underlying the presentinvention is to specify, for roughening the surface of a borehole, atool that does not exhibit the disadvantages described in the foregoingor at least exhibits them to a lesser extent, and in particular permitsroughening of a borehole surface in simple manner, wherein the influenceof the user is minimized and at the same time the comfort of applicationis increased.

The technical problem described in the foregoing is solved by a tool forroughening a borehole surface, with a coupling portion for clamping thetool in a drilling machine and a tool head for machining the boreholesurface, wherein cutting means disposed circumferentially on the toolhead are provided. The tool head has at least one slit that passesthrough from one side to the other and, starting from an end face of thetool head, extends axially along the longitudinal axis of the tool.

By the fact that the tool head is slit in axial direction at the endface, the tool head is subdivided into freely projecting arms, which areable to be resiliently deflected radially inward. This resilient radialinward deflection of the tool head permits introduction into a borehole.The circumferentially disposed cutting means may therefore be pressed inresiliently elastic manner in radial direction against the boreholesurface to be roughened. In this way, by introducing the tool into aborehole, it is possible to generate, between the tool and the boreholesurface, a radial preload force, which causes the cutting means topenetrate into the borehole surface during rotation of the tool. Theradial cutting forces are therefore generated by a resiliently elasticpreload, without necessitating a wobbling motion or eccentric motion ofthe tool. Thus the user merely has to execute a translatory movement ofthe tool corresponding to a drilling process. Consequently, thevibrations of the tool during the roughening process can be minimized.In addition, the wear of the cutting means can be reduced by the radialelasticity of the tool head. Thus the cutting means are able to avoidcollision structures such as rebar or hard rock during the rougheningprocess, by the fact that the cutting means are forced or resilientlydeflected in a direction facing radially inward upon contact with thesematerials.

In particular, the circumferentially disposed cutting means describe anenvelope circle, the diameter of which is larger than the nominaldiameter of the borehole to be machined. During introduction of such atool into the respective borehole, the arms with their circumferentiallydisposed cutting means are forced by the borehole surface in a directionfacing radially inward, so that the slit of the tool head is narrowed.In this case, the preload of the tool depends only on the dimensions ofthe tool and the nominal diameter of the borehole. Thus a defined,radial preload of the tool can be generated.

According to the invention, a tool is therefore specified that permitsroughening of a borehole surface in simple manner, wherein the influenceof the user is minimized and at the same time the comfort of applicationis increased.

Further configurations of the inventive tool are apparent from thedependent claims and the description of preferred exemplary embodiments.

According to one configuration of the tool, the tool head may have atleast two radially resilient arms, which extend along the slit and attheir free end portions adjacent to the end face carry thecircumferentially disposed cutting means. Due to the arrangement of thecutting means close to the end face, resilient deflection of the arms inthe direction of the longitudinal axis of the tool is favored and theborehole is roughened as far as the end. In particular, the axiallongitudinal extent of the slit may correspond to a multiple of theaxial longitudinal extent of the free end portion, on which the cuttingmeans are disposed. The further the slit reaches in axial direction intothe tool head, the greater is the leverage supplied by the arms, and soresilient deflection, in radially inward direction, of the cutting meansdisposed in the region of the end portions is facilitated.

According to an improvement of the tool, the tool head may have at leasttwo mutually intersecting slits that extend, starting from an end faceof the tool head, axially along the longitudinal axis of the tool.Consequently, the tool head may have four arms extending along the slitsand respectively carrying the cutting means circumferentially. Theradial elasticity of the tool increases with the number of slits, and sothe tool can be introduced particularly easily into a borehole.

According to a further configuration of the invention, a multiplicity ofmutually intersecting slits may be provided in the region of the toolhead.

In order to achieve a different penetration depth of the circumferentialcutting means during the roughening process, a first slit may have agreater length along the longitudinal axis of the tool than a secondslit.

The slits of the tool head may intersect one another at an angle smallerthan or equal to 90°. In particular, therefore, the slits may extendthrough the tool head substantially perpendicular to one another.Alternatively, to adapt the radial stiffness of individual arms, anangular position of the slits deviating from 90° may be provided, sothat the arms have different cross sections. For example, if two slitsinclude an angle smaller than 90°, four arms are formed. In this case afirst pair of arms disposed opposite one another in pairs has a smallerwall thickness than a second pair of arms disposed next to these arms.In this way, the radial stiffness of the arms and consequently the depthof penetration of the cutting members during the roughening process canbe adjusted.

According to a further construction, the tool is configuredsymmetrically. In particular, the tool may be constructed in such a waythat the tool has homogeneous radial stiffness, so that dynamic loadsduring the roughening process or imbalance due to preloading of the toolare avoided. Thus at least two arms may be formed with point symmetryrelative to a longitudinal axis of the tool. Alternatively oradditionally, at least two arms may be formed with mirror symmetryrelative to a plane of the tool, wherein the longitudinal axis of thetool lies in the plane of the tool. In particular, a slit may be made insuch a way in the tool that at least two arms have substantiallyparallel flat planes facing one another.

For optimum functionality of the inventive tool, it may be necessary toconfigure the slits variably over the length. The slit width at the topend of the tool head is preferably dimensioned such that the two armsjust do not touch one another at maximum necessary resilient inwarddeflection of the cutting means. Thus the slit width depends on thenominal diameter of the borehole for which the inventive tool is to beused. The dimensioning of the slit width at the opposite end of theslit, i.e. at the bottom of the slit facing away from the end face ofthe tool head, defines the spring stiffness of the arms and maynecessarily be dimensioned smaller than the necessary slit width at thetop end of the tool head. This may be permitted, for example, via a stepchange in the slit profile. According to one construction of theinventive tool, the slit, starting from the top end of the tool head,has a greater width over a region in the direction of the longitudinalaxis of the tool than over the connecting region in the direction of itsbottom facing away from the front end. A tool configured in such a wayis suitable in particular for small borehole diameters.

According to an improvement of the inventive tool, the slit may have aconcave rounding at its bottom facing away from the end face. Thisrounding may be formed by a through bore made in the tool head,especially transversely relative to the longitudinal extent of the slit.By means of the rounding, a notch effect in the region of the bottom ofthe slit is reduced and the spring stiffness or the force of pressing ofthe cutting means against the borehole wall is adjusted.

The cutting means of the tool may comprise at least two radiallyextending carbide and/or diamond pins pointing away from thelongitudinal axis of the tool. Preferably, the pins each form onegeometrically specific cutter, thus permitting well-defined introductionof furrows or undercuts in the borehole surface. Thus it is possible tomake the pins used from a hard material and the arms from an elasticmaterial. At their radial outer ends, the pins have especially afrustoconical or hemispherical shape.

According to an improvement of the inventive tool, a multiplicity ofcarbide and/or diamond pins are provided, which are distributed in axialdirection and/or circumferentially on the tool head. For example, an armmay carry one single or a multiplicity of carbide pins. The carbide pinsmay be distributed circumferentially on the ridge or be disposed axiallyone after the other along the longitudinal direction of the tool. Forexample, two or more, especially three carbide pins may be provided onone ridge. The carbide pins may be densely packed in axial direction ordisposed closely adjacent to one another in an end portion of the ridgeassociated with the end face. Alternatively or additionally, the carbidepins may be disposed on an outer shell surface of the ridge at the sameaxial height but distributed circumferentially with an angular spacingfrom one another.

According to a further configuration of the tool, the tool head may havesubstantially circular cylindrical shape. The diameter of the outershell surfaces bounding the cylinder in radial direction is preferablysmaller than the nominal diameter of a borehole to be machined.Preferably, carbide and/or diamond pins disposed on the outer shellsurface and pointing outwardly in radial direction define the maximumdiameter of the tool, wherein the diameter of an envelope circle definedby the carbide or diamond pins is in particular larger than the nominaldiameter of the borehole to be machined. By the introduction of one ormore slits in the end face, the cylindrical tool head can be subdividedinto several arms, the outer shell surfaces of which describe circularsegments, such as semicircles or quarter circles, in a sectiontransverse to the longitudinal axis of the tool. In the region of aslit, these arms may have flat faces facing one another.

In addition, an advantageous improvement of the tool may be specified tothe effect that the coupling portion is disposed at a first end of atool shank and the tool head at an opposite second end of the toolshank, wherein the tool shank is at least twice as long, preferably atleast three times as long as the tool head in axial direction. With atool configured in this way, even the machining of deeper boreholes iseasily possible.

The diameter of the tool shank may correspond to the diameter of thetool head or be smaller than the diameter of the tool head.Independently of this, the diameter of the tool shank may furthercorrespond to the diameter of the coupling portion or be smaller thanthe diameter of the coupling portion. In this way, the tool can beconfigured to be lightweight and flexible, wherein the handling duringoperation is improved on the whole.

According to an improvement of the inventive tool, the slit is filled atleast in portions with an elastic filling material, especially anelastomer, in order to increase the radial preload forces duringoperation of the tool. The radial stiffness of the tool head can beincreased by the filling material. Furthermore, the filling material canbe used to damp vibrations or oscillations during machining of theborehole surface.

For optimization of the elastic properties, the tool head may have acylindrical recess, especially a bore, which starts from the end face,extends along the longitudinal axis of the tool and may reach as far asthe shank extending to the tool head.

According to a further configuration of the inventive tool, ageometrically determined cutting geometry, especially in the manner of adrill, is provided in addition to the circumferential cutting means inthe region of the tool head. Thus the end face of the tool head may havea drill tip split or slit axially along the longitudinal direction ofthe tool. In particular, two arms, which respectively carry cuttingmeans circumferentially in the region of an outer shell surface, mayrespectively form a cutting wedge at the end face. In this way, axialpenetration of the tool can be facilitated, especially in the region ofa borehole bottom. The cutting edge may be formed by a cutting plateattached to the ridge or by the ridge itself.

In this connection, the nominal diameter of the borehole may preferablybe smaller than the diameter of an envelope circle defined by thecircumferential cutting means. In such a case, the tool is elasticallybraced resiliently in radial direction when the tool is introduced intothe borehole, wherein the slit of the tool is narrowed. During rotationof the tool, these bracing forces cause the cutting means to penetrateinto the borehole surface while roughening the borehole surface. In theprocess, the operator is able to introduce undercuts into the boreholesurface by executing a purely translatory movement of the tool along alongitudinal axis of the borehole.

Starting from a borehole bottom, the borehole surface can be roughenedover the entire length measured in axial direction. In this case thereis no need for a subsequent cleaning treatment of the borehole, forexample by flushing or blowing out, since an adequately large roughenedsurface is available despite the accumulation of drilling dust at theborehole bottom.

The invention will be described in more detail hereinafter on the basisof a drawing that schematically illustrates exemplary examples, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first configuration of an inventive tool in a perspectiveview, a front view and a reduced side view;

FIG. 2 shows a second configuration of an inventive tool in aperspective view, a front view and two side views;

FIGS. 3a-3c show variants for arrangement of the slits in the region ofthe tool head in perspective and front views;

FIGS. 4a, 4b show variants for arrangement of carbide pins in the regionof the tool head;

FIG. 5 shows a configuration of the tool head with a cutting geometry

FIG. 6 shows a configuration of the tool head with a step change in theslit profile.

DETAILED DESCRIPTION

FIG. 1 shows a first configuration of a tool 10 for roughening aborehole surface.

Tool 10 has a coupling portion 12 for clamping tool 10 in a drillingmachine (not illustrated), a tool head 14 for machining a boreholesurface (not illustrated) and a tool shank 16 joining a coupling portion12 and tool head 14. Coupling portion 12 is disposed at a first end andtool head 14 at a second end, opposite the first end, of tool shank 16.

Tool shank 16 is more than twice as long as tool head 14 along an axialdirection a. The diameter of tool shank 16 corresponds to that ofcoupling portion 12 and is smaller than the diameter of tool head 14.

Tool head 14 is substantially cylindrical and has circumferentiallydisposed, radially protruding carbide pins 18. Carbide pins 18 arefacing radially outward and extend in a radial direction r2 transverseto axial direction a.

Tool head 14 has a slit 20 which, starting from an end face 22 of toolhead 14, extends axially along longitudinal axis A of the tool as wellas laterally from one to an opposite shell-surface portion, meaning thatit passes though from one side to the other and divides tool head 14.

Thus tool head 14 has two arms 24 extending along slit 20. At their freeend portions 26 adjacent to end face 22, arms 24 carry circumferentialcarbide pins 18.

As an example, three carbide pins 18 disposed adjacent to one another inaxial direction are provided on each arm. It will be understood thatdiamond pins may be provided alternatively or additionally as cuttingmeans.

Arms 24 are configured with mirror symmetry relative to a plane definedby axial direction a and radial direction r1. Arms 24 have flat faces28, which face one another and are disposed with constant spacing fromone another. In other words, slit 20 has a substantially constant gapwidth.

At its bottom facing away from end face 22, the slit has a concaverounding 30. Rounding 30 is a radial through-bore. Tool head 14 has acylindrical recess 32, which is constructed here as a bore, that startsfrom end face 22 and extends along longitudinal axis A of the tool.

For roughening a borehole surface, tool 10 is introduced with its toolhead 14 into a borehole. For this purpose, tool 10 is clamped withcoupling portion 12 in a drilling machine. The nominal diameter of theborehole is smaller than the diameter of an outer envelope circle oftool 10 defined by carbide pins 18. During introduction of tool head 14into the borehole, carbide pins 18 are therefore forced radially inwardby the borehole surface, in the direction of longitudinal axis A of thetool. In this way, slit 20 is narrowed. In this condition, carbide pins18 bear on the borehole surface and are resiliently braced elasticallyagainst the borehole surface via arms 24, which are elastically bentinwardly.

Rotation of the tool imposed by the drilling machines causes carbidepins 18 to penetrate into the borehole surface and introduce furrows orundercuts in the borehole surface. The borehole may be a blind hole.

For roughening the borehole surface, tool 10 merely has to be introducedby translation along longitudinal axis A of the tool into the borehole.The radial cutting forces are achieved solely by the resiliently elasticpreload of tool head 14, and so no radial force has to be transmittedinto tool 10 by the user.

FIG. 2 shows a second configuration of a tool 10. The basic structureand the manner of functioning of tool 10 illustrated in FIG. 2correspond substantially to those of the embodiment described in theforegoing with reference to FIG. 1. Like features are therefore denotedhereinafter by like reference symbols, and only differences between theindividual tools will be discussed.

Compared with FIG. 1, tool 10 illustrated in FIG. 2 has a modifiedcoupling portion 12. In the exemplary embodiment illustrated here, abore 32 at the end face is omitted, and so only a slit 20 is present.Carbide pins 18 disposed in end portion 26 are more closely packed inaxial direction a than in the example described in the foregoing.

FIGS. 3a to 3c illustrate three different variants for arrangement ofslits 20 in the region of tool head 14. FIG. 3a shows a tool head 14 ina perspective view and a front view. Tool head 14 has two slits 20 thatintersect one another in the center axis of the tool, so that four arms22 in total are formed, each carrying one carbide pin 18. Tool head 14has symmetrical structure.

FIG. 3b likewise shows a tool head 14 with two mutually intersectingslits 20, but wherein one of the slits 20 has a greater length along thelongitudinal axis of the tool than does the other slit.

FIG. 3c shows a further variant of a tool head 14, which differs fromthe variants described in the foregoing in that slits 20 do not passthrough tool head 14 at right angles but instead are oriented obliquelyrelative to one another. Arms 24, disposed opposite to one another inpairs, therefore have different wall thicknesses and cross sections, ascan be inferred from the front view.

FIGS. 4a and 4b show variants for arrangement of carbide pins 18 in theregion of tool head 14. FIG. 4a shows an axial arrangement of thecarbide pins, while FIG. 4b represents a circumferential distribution,in which the carbide pins are disposed with angular spacing from oneanother relative to the longitudinal axis of the tool.

FIG. 5 shows a configuration of tool head 14 with a cutting geometry 34.Arms 24 are shaped at the end face in the manner of a drill, wherein adrill tip split by slit 20 is formed along longitudinal axis A of thetool.

Naturally, tool head 14 may be manufactured separately and mounted onthe shank detachably or permanently.

FIG. 6 shows a configuration of tool head 14 with a step change in theslit profile, so that slit 20, 20′ has a different slit width alonglongitudinal axis A of the tool, wherein the slit, starting from the topend of the tool head, has a greater width over a region (slit 20) in thedirection of the longitudinal axis of the tool than over the connectingregion (slit 20′) in the direction of its bottom facing away from thefront end. Due to the broader slit region 20, arms 24 at the end of thetool head are able to be deflected resiliently inward sufficiently,corresponding to the borehole diameter, in the direction of longitudinalaxis A of the tool, especially in the case of small borehole diameters,wherein the spring force is adjusted by the narrower slit 20′.

The invention claimed is:
 1. A tool for roughening a borehole surface,comprising: a coupling portion to clamp the tool in a drilling machine;and a tool head to machine the borehole surface, wherein the tool headcomprises a cutter that is disposed on a circumferential surface of thetool head, wherein the tool head includes at least one slit which passesthrough from one side of the circumferential surface of the tool head toanother side of the circumferential surface of the tool head, the atleast one slit starting from an end face of the tool head and extendingaxially along a longitudinal axis of the tool to define at least twoarms parallel to the longitudinal axis, wherein the arms are to defectinwardly in a radial direction when the borehole surface is beingmachined, and wherein the cutter comprises at least two pins pointingradially away from the longitudinal axis of the tool and distributed inaxial direction and/or circumferentially on the tool head.
 2. The toolaccording to claim 1, wherein the tool head has at least two radiallyresilient arms, which extend along the slit and at free end portionsthereof, adjacent to the end face carry the cutter.
 3. The toolaccording to claim 1, wherein the tool head has at least two mutuallyintersecting slits that extend, starting from an end face of the toolhead, axially along the longitudinal axis of the tool.
 4. The toolaccording to claim 3, wherein a first slit has a greater length alongthe longitudinal axis of the tool than a second slit.
 5. The toolaccording to claim 3, wherein the slits intersect one another at anangle smaller than or equal to 90°.
 6. The tool according to claim 1,wherein at least portions of the tool are configured symmetrically. 7.The tool according to claim 1, wherein the slit includes a concaverounding at bottom facing away from the end face thereof.
 8. The toolaccording to claim 1, wherein the at least two pins are carbide and/ordiamond pins.
 9. The tool according to claim 1, wherein the tool head issubstantially cylindrical and/or has a cambered outer contour.
 10. Thetool according to claim 1, wherein the coupling portion is present at afirst end of a tool shank and the tool head is at an opposite second endof the tool shank, and wherein the tool shank is at least twice as longas the tool head in axial direction.
 11. The tool according to claim 10,wherein the tool shank has a diameter smaller than that of the toolhead.
 12. The tool according to claim 1, wherein the slit comprises, atleast in portions, an elastic filling material.
 13. The tool accordingto claim 1, wherein the tool head has a cylindrical recess that startsfrom the end face and extends along the longitudinal axis of the tool.14. The tool according to claim 1, wherein a geometrically determinedcutting geometry is provided in the region of the tool head, in additionto the cutter.
 15. The tool according to claim 1, wherein the at leastone slit extends through a center axis of the tool.
 16. The toolaccording to claim 1, wherein the at least one slit has different widthsalong the longitudinal axis of the tool.
 17. The tool according to claim1, wherein the at least two pins comprises three or more carbide and/ordiamond pins.
 18. The tool according to claim 1, wherein the couplingportion is present at a first end of a tool shank and the tool head isat an opposite second end of the tool shank, and wherein the tool shankis at least three times as long as the tool head in axial direction. 19.The tool according to claim 1, wherein the slit includes an elastomer.20. The tool according to claim 1, wherein the tool head has a bore thatstarts from the end face and extends along the longitudinal axis of thetool.